The reaction of (S)-3-N-Cbz-4-pentenoic acid with iodine in acetonitrile in the presence of AgOTf gave the cis-iodo-lactone 6 in excellent yield and in a highly diastereoselective manner. The substitutions of the iodine in 6 by different Grignard reagents in the presence of CuI and the subsequent conversions into the functionalized syn-γ-hydroxy-β-amino acids have been investigated. By the above reaction sequence, (3S,4S)-3-amino-4-hydroxy-5-cyclohexyl pentanoic acid was synthesized with high enantioselectivity.